Synthesis of 7-oxa-phomopsolide E and its C-4 epimer

A flexible, enantioselective route to highly functionalized α,β-unsaturated δ-lactones has been applied to the synthesis of 7-oxa-phomopsolide E and its C-4 epimer. This approach relies on the application of the Noyori asymmetric hydrogenation of furyl ketone to produce the secondary furyl alcohol in high enantioexcess, which can be stereoselectively transformed into α,β-unsaturated-δ-lactones by a short, highly diastereoselective oxidation and reduction sequence. DCC and Mitsunobu coupling were used to introduce the side chains of the two natural product analogs.